Cleaning blade member

ABSTRACT

An object of the present invention is to provide a cleaning blade member exhibiting excellent mechanical properties including wear resistance. The cleaning blade member formed of a rubber-like elastic material produced through reaction of a long-chain polyol having a number average molecular weight of 1,500 to 3,800, an isocyanate, and an isocyanurate derivative having two or more OH groups, wherein the isocyanurate derivative is employed in an amount of 0.5 to 15 parts by weight with respect to 100 parts by weight of the long-chain polyol.

The entire disclosure of Japanese Patent Applications Nos. 2006-155288 filed Jun. 2, 2006 and No. 2007-140 filed May 28, 2007 is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cleaning blade member and, more particularly, to a cleaning blade member for removing toner deposited on a toner image carrier employed in an electrophotographic process such as a photoconductor or a transfer belt, on which a toner image is formed and which transfers the formed image to an image receptor.

2. Background Art

Generally, in an electrophotographic process, electrophotographic apparatus parts such as an electrophotographic photoreceptor and a transfer belt are used cyclically and repeatedly, and toner deposited thereon is removed by means of a cleaning blade. The cleaning blade, which generally comes into contact with a photoreceptor over a long period of time, is required to have excellent wear resistance. Currently, members for use in such a cleaning blade are made of polyurethane. Polyurethane is employed because it has excellent wear resistance, exhibits sufficient mechanical strength without incorporation of additives such as a reinforcing agent thereinto, and does not stain objects. However, polyurethane has a drawback in that physical properties thereof vary with temperature.

Hitherto, various cleaning blades made of polyurethane have been developed. Japanese Patent Application Laid-Open (kokai) No. 2001-265190 discloses a cleaning blade made of hardened polyurethane which exhibits a tensile strength at 50° C. of 12 MPa or more, a tanδ peak temperature of 15° C. or lower, and a hardness of 80° or less. Chipping of the cleaning blade under high-temperature conditions is effectively prevented without impairing cleaning performance under low-temperature conditions. Thus, the cleaning blade exhibits excellent cleaning performance over a wide temperature range.

Japanese Patent Application Laid-Open (kokai) No. 9-274416 discloses a blade, for use in electrophotographic apparatuses, employing a polyurethane sheet which is produced by mixing a bi-functional polyol having a number average molecular weight of 1,000 to 3,000 and a tri-functional polyol having a number average molecular weight of 92 to 980, to thereby provide a polyol mixture having an average functionality of 2.02 to 2.20; mixing the polyol mixture with a diisocyanate compound having an isocyanate group content of 5 to 20%, to thereby prepare a prepolymer; adding to the prepolymer a cross-linking agent in an amount so as to adjust the OH/NCO ratio (eq.) to 0.90 to 1.05 and a reaction accelerator in an amount of 0.01 to 1.0 parts by weight with respect to 100 parts by weight of the prepolymer; and allowing the mixture to react.

However, wear resistance and other properties of the aforementioned blades are not satisfactory and, therefore, are to be further improved.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the present invention is to provide a cleaning blade member exhibiting excellent mechanical properties including wear resistance.

Accordingly, in a first mode of the present invention in order to attain the object, there is provided a cleaning blade member formed of a rubber-like elastic material produced through reaction of a long-chain polyol having a number average molecular weight of 1,500 to 3,800, an isocyanate, and an isocyanurate derivative having two or more OH groups, wherein the isocyanurate derivative is employed in an amount of 0.5 to 15 parts by weight with respect to 100 parts by weight of the long-chain polyol.

A second mode of the present invention is directed to a specific embodiment of the cleaning blade member according to the first mode, wherein the long-chain polyol has a number average molecular weight of 1,650 to 3,000.

A third mode of the present invention is directed to a specific embodiment of the cleaning blade member according to the first mode, wherein the isocyanurate derivative is employed as a cross-linking agent or a chain-extender.

A fourth mode of the present invention is directed to a specific embodiment of the cleaning blade member according to the second mode, wherein the isocyanurate derivative is employed as a cross-linking agent or a chain-extender.

A fifth mode of the present invention is directed to a specific embodiment of the cleaning blade member according to the first mode, wherein the long-chain polyol contains a polyester-polyol having an ester concentration of 6.85±0.25 mmol/g, the ester concentration being defined by the following relation:

ester concentration (mmol/g)=(amount of ester groups by mole)/(weight of polyester-polyol).

A sixth mode of the present invention is directed to a specific embodiment of the cleaning blade member according to the fifth mode, wherein the polyester-polyol is formed through dehydration condensation between at least one diol component selected from among nonanediol and methyloctanediol and at least one dibasic acid selected from among adipic acid, sebacic acid, and azelaic acid.

A seventh mode of the present invention is directed to a specific embodiment of the cleaning blade member according to the first mode, which has a rubber hardness as stipulated by JIS A of 65 to 850.

An eighth mode of the present invention is directed to a specific embodiment of the cleaning blade member according to the first mode, which has a rebound resilience of 40 to 80%, as determined at 25° C.

According to the present invention, there can be provided a cleaning blade member exhibiting excellent mechanical properties including wear resistance.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graph showing the results of Test Example 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The cleaning blade member of the present invention is formed of a rubber-like elastic material produced through reaction of a long-chain polyol having a number average molecular weight of 1,500 to 3,800, an isocyanate, and an isocyanurate derivative having two or more OH groups, wherein the isocyanurate derivative is employed in an amount of 0.5 to 15 parts by weight with respect to 100 parts by weight of the long-chain polyol. When the isocyanurate derivative having two or more OH groups is employed in an amount of 0.5 to 15 parts by weight with respect to 100 parts by weight of the long-chain polyol, and reacted with the long-chain polyol and the isocyanate, a cleaning blade member exhibiting excellent wear resistance can be provided. Unless otherwise specified, the unit “part(s)” denotes “part(s) by weight.”

The long-chain polyol employed in the present invention has a number average molecular weight of 1,500 to 3,800, preferably 1,650 to 3,000. When the number average molecular weight falls outside the above range, a cleaning blade member exhibiting predetermined properties cannot be yielded.

No particular limitation is imposed on the type of the long-chain polyol, so long as the molecular weight thereof falls within the above range. Examples of the long-chain polyol include polyester-polyols formed through dehydration condensation between a diol component and a dibasic acid; polycarbonate-polyols formed through dehydration condensation between a diol and an alkyl carbonate; caprolactone-derived polyols; and polyether-polyols.

The long-chain polyol employed in the present invention preferably contains a polyester-polyol. The polyester-polyol preferably has an ester concentration of 6.85±0.25 mmol/g, the ester concentration being defined by the following relation:

ester concentration (mmol/g)=(amount of ester groups by mole)/(weight of polyester-polyol).

An ester concentration falling within the above range is preferred for attaining high mechanical strength as well as low temperature-dependency of rebound resilience and other properties.

The polyester-polyol employed in the invention and having an ester concentration falling within the above range is preferably a polyester-polyol formed through dehydration condensation between a diol component and a dibasic acid. However, polyester-polyols other than those formed through dehydration condensation between a diol component and a dibasic acid may also be employed so as to attain the aforementioned properties, so long as the polyester-polyols have an ester concentration falling within the above range.

Examples of the polyester-polyol employed in the present invention include polyester-polyols formed from, in combination, a diol component such as ethylene glycol, butanediol, hexanediol, nonanediol, decanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2,4-diethyl-1,5-pentanediol, butylethylpropanediol, or 2-methyl-1,8-octanediol, and a dibasic acid such as adipic acid, sebacic acid, azelaic acid, a dimer acid, or a hydrogenated dimer acid, with these polyester-polyols having an ester concentration satisfying the aforementioned conditions. Specific examples include nonanediol adipate, 2-methyl-1,8-octanediol adipate, decanediol adipate, hexanediol azelate, nonanediol azelate, 2-methyl-1,8-octanediol azelate, decanediol azelate, butanediol sebacate, hexanediol sebacate, nonanediol sebacate, 2-methyl-1,8-octanediol sebacate, decanediol sebacate, glycol dimer acid esters, and glycol hydrogenated dimer acid esters. The diol components or the dibasic acids may be used singly or in combination.

So long as the above conditions are satisfied, a lactone such as ε-caprolactone or δ-valerolactone may be polyadded or co-polymerized. In other words, there may also be employed a random copolymer which has been formed through copolymerization of a lactone during dehydration condensation between a diol component and a dibasic acid, or a polyol which has been formed, for example, polyaddition of a lactone to a dehydration condensation product. Through employment of a lactone, rebound resilience at low temperature can further be enhanced.

Particularly, a polyester-polyol formed through dehydration condensation between at least one diol component selected from among nonanediol and methyloctanediol, and at least one dibasic acid selected from among adipic acid, sebacic acid, and azelaic acid is preferred from the viewpoint of performance and cost. More particularly, at least one diol component selected from among 1,9-nonanediol and methyl-1,8-octanediol is preferred. Single use of 1,9-nonanediol is not preferred, since crystallinity of the produced polyurethane is excessively high. Therefore, in a preferred mode, methyl-1,8-octanediol is used singly or in combination with 1,9-nonanediol. Needless to say, a modified combination which includes the aforementioned diol component and dibasic acid as a predominant reactant, and another glycol and dibasic acid are also preferably employed. As used herein, the diol “methyl-1,8-octanediol” is an octanediol species having a methyl group at a position other than 1- and 8-positions, and a typical example thereof is 2-methyl-1,8-octanediol. However, other methyl-1,8-octanediol species may also be employed.

The isocyanate which is reacted with the polyol preferably has a somewhat non-rigid molecular structure. Examples of such isocyanates include 4,4′-diphenylmethane diisocyanate (MDI), 2,6-toluene diisocyanate (TDI), 1,6-hexane diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), and 3,3-dimethylphenyl-4,4-diisocyanate (TODI). Of these, MDI is preferred.

The isocyanurate derivative employed in the present invention has two or more OH groups, which allow the derivative to react with an isocyanate and be integrally incorporated into a polyurethane matrix. The thus-formed polyurethane attains desired physical properties. Examples of the isocyanurate derivative having two or more OH groups include tris(2-hydroxyethyl) isocyanurate having a molecular weight of 261 (Tanac, product of Nissan Chemical Industries, Ltd.).

The isocyanurate derivative of the present invention is used in an amount of 0.5 to 15 parts with respect to 100 parts of the long-chain polyol. When the amount of isocyanurate derivative is less than 0.5 parts, the effect of enhancing wear resistance is insufficient, whereas when the amount is in excess of 15 parts, the isocyanurate derivative aggregates, thereby failing to form the rubber-like elastic material.

The aforementioned isocyanurate derivative having two or more OH groups is preferably employed as a cross-linking agent or a chain-extender. Preferably, a cross-linking agent or a chain-extender other than the isocyanurate derivative is also employed. The isocyanurate derivative of the present invention may also serve as a part of the cross-linking agent or the chain-extender. Since the isocyanurate derivative has high thermal decomposition temperature, no heat-induced breakage of molecular chains under friction is considered to occur. Therefore, when the isocyanurate derivative is employed as a cross-linking agent or a chain-extender, a cleaning blade member of excellent wear resistance can be provided.

Although no particular limitation is imposed on the type of the cross-linking agent and chain-extender used in combination with the isocyanurate derivative, a short-chain polyol having a number average molecular weight of 500 or less is preferably employed. Examples of the cross-linking agent and chain-extender include linear-chain glycols having a C2 to C12 main chain such as ethylene glycol, 1,3-propanediol, and 1,4-butanediol; diols having a C≦12 side chain such as neopentyl glycol, and 3-methyl-1,5-pentanediol; diols having a C≦12 unsaturated group such as 3-allyloxy-1,2-propanediol; C≦20 diols having an aromatic ring such as 1,4-bis(hydroxyethoxy)benzene and p-xylene glycol; alicyclic diols such as cyclohexanediol and cyclohexanedimethanol; triols such as trimethylolethane, trimethylolpropane, and glycerin; and polyols having 4 or more functionalities, such as pentaerythritol and sorbitol. Needless to say, these short-chain polyols may be used in combination of two or more species.

Of these, bi-functional polyols such as 1,4-butanediol and 1,3-propanediol are particularly preferred, from the viewpoint of performance and cost.

The aforementioned long-chain polyol, the isocyanurate derivative, the cross-linking agent or chain-extender, and the isocyanate are mixed, and the mixture is allowed to react, to thereby produce polyurethane. Through modifying the amount (parts) of isocyanate, the balance of the cross-linking agent or chain-extender, and other conditions, a cleaning blade member of more excellent wear resistance can be produced.

The cleaning blade member according to the present invention preferably has a rubber hardness as stipulated by JIS A of 65 to 85°. When the hardness is lower than 65°, wear resistance decreases, and detachment of the blade from a support causing cleaning failure tends to occur, whereas when the hardness is in excess of 85°, the blade member is in contact with a photoconductor at higher pressure, resulting in wearing of the photoconductor.

The cleaning blade member of the invention preferably has a rebound resilience of 40 to 80%, as determined at 25° C. When the rebound resilience is lower than 40%, cleaning failure occurs, whereas when the rebound resilience is in excess of 80%, anomalous sound (so-called squeaky sound) generates during cleaning by means of the cleaning blade.

The rubber-like elastic material employed in the present invention may be produced through a method typically employed for producing polyurethane, such as the prepolymer method and the one-shot method. In the present invention, the prepolymer method is preferred, since a polyurethane having excellent mechanical strength and wear resistance can be produced. However, no particular limitation is imposed on the production method.

The rubber-like elastic material may be molded through the centrifugal molding method. When the centrifugal molding method is employed, the air side of the molded rubber-like elastic material is preferably brought into contact with a photoconductor.

The thus-produced polyurethane (rubber-like elastic material) pieces are subjected to cutting or a similar process, to thereby form cleaning blade members having predetermined dimensions. Through bonding each cleaning blade member to a support member by use of an adhesive or a similar agent, a cleaning blade product is fabricated.

EXAMPLES

The present invention will next be described in detail by way of examples, which should not be construed as limiting the invention thereto.

Example 1

A polyol (PCL 220, product of DIC, molecular weight: 2,000) (100 parts), produced through ring-opening polymerization of ε-caprolactam, and 4,4′-diphenylmethane diisocyanate (MDI) (27 parts) were mixed with stirring at 140° C. for 10 minutes. To the mixture, tris(2-hydroxyethyl) isocyanurate (Tanac, product of Nissan Chemical Industries, Ltd.) (0.9 parts), which is an isocyanurate derivative having three OH groups, was added, followed by stirring for five minutes. Subsequently, 1,4-butanediol (1,4-BD) (4.2 parts) was further added to the mixture with stirring. The thus-prepared mixture was cast into a mold which was maintained at 150° C., and heated for 20 minutes for reaction, to thereby form a cured rubber-like elastic material. The formed elastic material was cut into pieces (width: 14 mm), and each piece was affixed to a metal sheet, to thereby produce a cleaning blade of Example 1.

Example 2

The procedure of Example 1 was repeated, except that a polyol (PCL 230, product of DIC, molecular weight: 3,000), produced through ring-opening polymerization of ε-caprolactam, was used instead of the polyol (PCL 220, product of DIC, molecular weight: 2,000), produced through ring-opening polymerization of ε-caprolactam, and the amounts of Tanac and 1,4-BD were changed to 5 parts and 4 parts, respectively, to thereby produce a cleaning blade of Example 2.

Example 3

The procedure of Example 1 was repeated, except that a polyol (O-2010, product of Kuraray Co., Ltd., molecular weight: 2,000), produced through dehydration concentration among nonanediol, methyloctanediol, and adipic acid, was used instead of the polyol (PCL 220, product of DIC, molecular weight: 2,000), produced through ring-opening polymerization of ε-caprolactam, and the amounts of MDI, Tanac, and, 1,4-BD were changed to 40 parts, 5.5 parts, and 6.5 parts, respectively, to thereby produce a cleaning blade of Example

Example 4

The procedure of Example 3 was repeated, except that a polyol (PTMG 2000, product of Hodogaya Chemical Co., Ltd., molecular weight: 2,000), produced through polymerization of tetrahydrofuran (THF), was used instead of the polyol (PCL 220, product of DIC, molecular weight: 2,000), produced through ring-opening polymerization of ε-caprolactam, to thereby produce a cleaning blade of Example 4.

Example 5

The procedure of Example 3 was repeated, except that 3,3-dimethylphenyl-4,4-diisocyanate (TODI) was used instead of MDI, to thereby produce a cleaning blade of Example 5.

Example 6

The procedure of Example 1 was repeated, except that a polyol (PTMG 1650, product of Hodogaya Chemical Co., Ltd., molecular weight: 1,650) was used instead of the polyol (PCL 220, product of DIC, molecular weight: 2,000), produced through ring-opening polymerization of ε-caprolactam, and the amounts of MDI, Tanac, and, 1,4-BD were changed to 48 parts, 9 parts, and 7 parts, respectively, to thereby produce a cleaning blade of Example 6.

Comparative Example 1

The procedure of Example 3 was repeated, except that TMP (2.8 parts) was used instead of Tanac, and the amount of 1,4-BD was changed to 6.6 parts, to thereby produce a cleaning blade of Comparative Example 1.

Comparative Example 2

The procedure of Example 4 was repeated, except that TMP (2.8 parts) was used instead of Tanac, to thereby produce a cleaning blade of Comparative Example 2.

Comparative Example 3

The procedure of Example 1 was repeated, except that the amounts of 1,4-BD and Tanac were changed to 4.5 parts and 0.4 parts, respectively, to thereby produce a cleaning blade of Comparative Example 3.

Comparative Example 4

The mixing procedure of Example 1 was repeated, except that MDI (60 parts), Tanac (16.4 parts), and 1,4-BD (6.9 parts) were used.

Test Example 1

Test samples were produced from rubber-like elastic materials produced in the Examples and Comparative Examples. Rebound resilience of each sample was determined at 25° C. by means of a Lubke pendulum rebound resilience tester in accordance with JIS K6255, and rubber hardness (JIS A) of the sample was determined at 25° C. in accordance with JIS K6253. Table 1 shows the results.

Test Example 2 Wear Resistance

Each of the cleaning blades of the Examples and the Comparative Examples was pressed against a photoconductor, and the photoconductor was continuously rotated by means of a drive motor at a circumferential speed of 125 mm/sec for 90 minutes under NN conditions (23° C., 50%) or LL conditions (10° C., 30%), while no paper sheet was conveyed. After completion of the operation, the wear condition of an edge portion of the cleaning blade was observed under a microscope, and the amount of wear was microscopically determined. Toner was applied by means of a brush onto the photoconductor every 15 minutes. The results are shown in Table 1 and FIG. 1.

<Test Conditions>

Press conditions; Abutting angle: 25 deg., Pressure: 0.3 N/cm

Photoconductor; OPC (coated with initial lubricant) Testing time; 90 min Microscopy conditions;

Microscope: VH-7000 (KEYENCE Corporation),

-   -   magnification: ×450

Measurement points: 5 points per cleaning blade (i.e., points 20 mm from the respective ends, points 80 mm from the respective ends, and the center point)

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Polyol PCL 220 PCL 230 0–2010 PTMG 2000 0–2010 PTMG 1650 Ester concentration 8.5 8.6 6.8 0 6.8 0 Isocyanate MDI MDI MDI MDI TODI MDI (parts) 27 27 40 40 40 48 Isocyanurate Tanac Tanac Tanac Tanac Tanac Tanac (parts) 0.9 5 5.5 5.5 5.5 9 diols 1,4-BD 1,4-BD 1,4-BD 1,4-BD 1,4-BD 1,4-BD (parts) 4.2 4 6.5 6.5 6.5 7 Other triols — — — — — — (parts) — — — — — — Hardness JIS A (°) 65 67 72 71 78 74 Rebound resilience (%) at 63 51 54 56 41 42 25° C. Wear width (μm) under NN 3 4 0 5 2 4 conditions Wear width (μm) under LL 12 9 0 5 2 6 conditions Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Comp. Ex. 4 Polyol 0–2010 PTMG 2000 PCL 220 PCL 220 Ester concentration 6.8 0 8.5 8.5 Isocyanate MDI MDI MDI MDI (parts) 40 40 27 60 Isocyanurate — — Tanac Tanac (parts) — — 0.4 16.4 diols 1,4-BD 1,4-BD 1,4-BD 1,4-BD (parts) 6.6 6.5 4.5 6.9 Other triols TMP TMP — — (parts) 2.8 2.8 — — Hardness JIS A (°) 69 70 62 * Rebound resilience (%) at 48 50 67 * 25° C. Wear width (μm) under NN 42 110 62 * conditions Wear width (μm) under LL 59 115 74 * conditions * The isocyanurate derivative aggregated in Comparative Example 4, thereby failing to form the rubber-like elastic material.

As is clear from Table 1, the cleaning blades of Examples 1 to 6 exhibited a wear width of 5 μm or less under NN conditions (23° C., 50%) and a wear width of 12 μm or less under LL conditions (10° C., 30%), showing remarkably excellent wear resistance. The cleaning blades also exhibited a hardness of 65 to 78° and a rebound resilience of 41 to 63% at 25° C.

In contrast, the cleaning blades of Comparative Examples 1 and 2, which had been formed from a composition that does not include isocyanurate derivative, exhibited excellent hardness and rebound resilience, but a wide wear width (i.e., very poor wear resistance) as shown in FIG. 1. The cleaning blade of Comparative Example 3, which had been formed from a composition containing an isocyanurate derivative in less than 0.5 parts with respect to 100 parts of a polyol, exhibited excellent hardness and rebound resilience, but poor wear resistance; i.e., a wear width of 62 μm under NN conditions (23° C., 50%) and a wear width of 74 μm under LL conditions (10° C., 30%). The wear resistance was not considerably improved, since the amount of incorporated isocyanurate derivative was small. Furthermore, in Comparative Example 4, an isocyanurate derivative was used in excess of 15 parts with respect to 100 parts of a polyol. Thus, the isocyanurate derivative aggregated, thereby failing to form the rubber-like elastic material. As described hereinabove, the cleaning blade member of the present invention, which is formed from a long-chain polyol having a number average molecular weight of 1,500 to 3,800 (100 parts), an isocyanurate derivative having two or more OH groups (0.5 to 15 parts), and an isocyanate, has been proven to exhibit excellent wear resistance. 

1. A cleaning blade member formed of a rubber-like elastic material produced through reaction of a long-chain polyol having a number average molecular weight of 1,500 to 3,800, an isocyanate, and an isocyanurate derivative having two or more OH groups, wherein the isocyanurate derivative is employed in an amount of 0.5 to 15 parts by weight with respect to 100 parts by weight of the long-chain polyol.
 2. A cleaning blade member as described in claim 1, wherein the long-chain polyol has a number average molecular weight of 1,650 to 3,000.
 3. A cleaning blade member as described in claim 1, wherein the isocyanurate derivative is employed as a cross-linking agent or a chain-extender.
 4. A cleaning blade member as described in claim 2, wherein the isocyanurate derivative is employed as a cross-linking agent or a chain-extender.
 5. A cleaning blade member as described in claim 1, wherein the long-chain polyol contains a polyester-polyol having an ester concentration of 6.85±0.25 mmol/g, the ester concentration being defined by the following relation: ester concentration (mmol/g)=(amount of ester groups by mole)/(weight of polyester-polyol).
 6. A cleaning blade member as described in claim 5, wherein the polyester-polyol is formed through dehydration condensation between at least one diol component selected from among nonanediol and methyloctanediol and at least one dibasic acid selected from among adipic acid, sebacic acid, and azelaic acid.
 7. A cleaning blade member as described in claim 1, which has a rubber hardness as stipulated by JIS A of 65 to 85°.
 8. A cleaning blade member as described in claim 1, which has a rebound resilience of 40 to 80%, as determined at 25° C. 